import React, { Component } from 'react';
import Temperature from "./Temperature";

function BoilingVerdict(props) {
    if (props.celsius >= 100) {
        return <p>水会烧开</p>;
    } else {
        return <p>水不会烧开</p>;
    }
}

function toCelsius(fahrenheit) {
    return (fahrenheit - 32) * 5 / 9;
}

function toFahrenheit(celsius) {
    return (celsius * 9 / 5) + 32;
}

function tryConvert(temperature, convert) {
    const input = parseFloat(temperature);
    if (Number.isNaN(input)) {
        return '';
    }
    const output = convert(input);
    const rounded = Math.round(output * 1000) / 1000;
    return rounded.toString();
}

class Calculator extends Component {

    constructor() {
        super();
        this.state = {
            temperature: '',
            scale: 'c'
        };
        this.handleCelsiusChange = this.handleCelsiusChange.bind(this);
        this.handleFahrenheitChange = this.handleFahrenheitChange.bind(this);
    }

    handleCelsiusChange(temperature) {
        console.log('handleCelsiusChange:', temperature);
        this.setState({scale: 'c', temperature});
    }

    handleFahrenheitChange(temperature) {
        console.log('handleFahrenheitChange:', temperature);
        this.setState({scale: 'f', temperature});
    }

    render() {
        const scale = this.state.scale;
        const temperature = this.state.temperature;
        const celsius = scale === 'f' ? tryConvert(temperature, toCelsius) : temperature;
        const fahrenheit = scale === 'c' ? tryConvert(temperature, toFahrenheit) : temperature;
        console.log(`scale: ${scale} temperature: ${temperature} celsius: ${celsius} fahrenheit: ${fahrenheit}`);

        return (
            <div>
                <Temperature scale="c" temperature={celsius} onTemperatureChange={this.handleCelsiusChange}/>
                <Temperature scale="f" temperature={fahrenheit} onTemperatureChange={this.handleFahrenheitChange}/>
                <BoilingVerdict celsius={parseFloat(celsius)}/>
            </div>
        );
    }
}

export default Calculator;